Question

93 CHM-153 Advance Study Program QUALITATIVE ANALYSIS OF GROUP II CATIONS DATE NAME 1. What is the reagent responsible for the formation of hydrogen sulfide (H2S)? 2. When the cations are separated into subgroups, what is the purpose of the potassium hydroxide, KOH? 3. Explain the function of the aluminum wire and the mercury (II) chloride when testing for tin. 4. When testing for antimony, what reagent prevents tin from reacting with the H2S to form SnS2? 5. What reagent is used to identify copper and explain its function.

Answer 1

1. Fes (Iron Il sulfide) as the chemical compound responsible for formation of Hal gas. Fes (Ion I Sulfide) + 2 Con. Hell Feel the sgast cag) when Felds reacts with a moles of conc. All it will produce Ison (I) chloride and hydrogensulfide gas. 2. When cations are separated in to subgroups. The sole of KOH (diluted) to is to neutralise the solution as it is acidic and dissolve the precipitate in gellow ammonium sulfide . Generally Ags, Abs, Big, cus, Cas are insoluble in yellow ammonium sulfide But As , Sons, etc. are soluble in ammonium sulfide. tyce

The precipitate of Sutt, sbts & as SnS ,Sb, sal are dissolve in dil koH by forming hydroxo - complex. SnS₂ 160 H So COH)] + 25 can) Sb2S3 + 80425blohnt 35 Cag) Generally cute and Bitz can not form hydroxo complex with dil koH. So do not dissolve in dil koH.

art 3. As Aluminium can reduce Set (tin Ty) state to Sot? (tin II), and is converted in to Al3t. 2A2+ 3 Suty 2013 + + 3 Sut? Cs) Caq) (wire) Then the solution of Sut2 is added to the mercury (II) chloride (HgCl), which can bring oxidation - Reduction (Redox) process Snt + 2Hgt tace" -> Sint caq) + Hig, e, C) (white)

Formation of white precipitate indicates that presence of Senty is confirmed. And the white precipitate is Hg2 Cl.

oxalic Acid (ott) is the reagent which can prevents tin (Son) from reacting with H₂S from SoS₂. Sos, compound's colour is similar to sb z's colour, so flost the soln is treated with oxalic and and Sath reacts reacts oxalic Acid to form stable complex of Snow Sonth + Goutha (cooff (So (6) +24+ A stable complex

By this way sold is free from Sath so, sbt can reacts with its to from bright arrange ppt 25 63 +3th scan) - Sb₂S- (aq) + 6(aq) (orange)